Phase 3 interim analysis: Russian COVID-19 vaccine shows 91.6% effectiveness

Gam-COVID-Vac, also known as Sputnik V, is an adenovirus-based heterologous recombinant SARS-CoV-2 vaccine that was well tolerated and showed 91.6% effectiveness against COVID-19 in people aged 18 and over Phase 3 interim analysis published in The Lancet.

In this randomized, double-blind, placebo-controlled phase 3 study ( identifier: NCT04530396) conducted in 25 hospitals and polyclinics in Moscow, Russia, researchers investigated whether a 2-dose Gam COVID Vac Safe and Safe Vaccine is effective in preventing COVID-19 from the day of the second dose or 21 days after the first dose.

The final analysis included 19,866 adults (98.5% whites; mean age 45.3 years) who were randomly selected in a 3: 1 ratio to receive either a vaccine (n = 14,964) or a placebo (n = 4902). These adults were divided into 5 age groups: 18 to 30 years, 31 to 40 years, 41 to 50 years, 51 to 60 years and over 60 years.

Participants in the vaccine and placebo cohorts were similar in terms of age, gender, and distribution of comorbidities. The median follow-up time was 48 days after the first dose (interquartile range) [IQR]39-58 days).

From the day of the second vaccine dose (day 21), 0.1% (16 / 14,964) of participants from the vaccine cohort and 1.3% (62/4902) of participants from the placebo group were confirmed to have COVID-19, which is a gave vaccine efficacy of 91.6% (95% CI, 85.6-95.2). The efficacy of the vaccine was 73.1% (95% CI, 63.7-80.1) at all times after dose 1, with similar rates of disease between the two cohorts up to 16-18 days after dose 1.

An under-analysis of 2,144 adults older than 60 years showed a vaccine effectiveness of 91.8% (95% CI, 67.1-98.3).

Immunogenicity analyzes 42 days after vaccination showed robust receptor binding domain (RBD) -specific antibodies and virus-neutralizing antibodies. Of the 342 participants who were analyzed for the presence of antibodies specific for the RBD of SARS-CoV-2 glycoprotein S in the vaccine group, RBD-specific immunoglobulin G was detected in 98% of participants (geometric mean titer, 8996; 95% CI, 7610-10.635; seroconversion rate 98.25%). Compared to the other age groups, the 18 to 30-year-olds responded more strongly (P = 0.0065).

Of the 72 participants who were analyzed for the presence of neutralizing antibodies in the vaccine group, the geometric mean titer was 44.5 (95% CI, 31.8-62.2) with a seroconversion rate of 95.83%.

The vaccine also induced a strong cellular immune response 28 days after vaccination compared to day 1. Of the 44 participants in the vaccine cohort analyzed, all had significantly higher IFN-γ secretion levels after antigen restimulation (median 32.77 pg / ml; IQR) 13 , 94-50.76).

Most of the adverse events reported were Grade 1 and the most common were flulike illness, injection site reactions, headache, and lethargy. None of the serious adverse events were considered to be related to vaccination. There were 4 deaths among the participants, but none were vaccine-related.

The study was limited by the small sample size within the different age groups, the exclusion of asymptomatic cases in the analysis, and the predominantly white population. In addition, the researchers were unable to assess the duration of protection due to the short follow-up period. The vaccine needs further study in various population groups, including pregnant women, immunocompromised patients, and children and adolescents.

Although the vaccine was approved for storage at 2 to 8 ° C, the liquid form of the vaccine was used in this study, which requires storage at -18 ° C.

Disclosure: Several authors of the study have stated that they are part of the pharmaceutical industry. See the original reference for a full list of what the authors said.


Logunov DY, Dolzhikova IV, Shcheblyakov DV, et al .; Gam-COVID-Vac vaccine experimental group. Safety and efficacy of a heterologous prime-boost COVID-19 vaccine based on rAd26 and rAd5 vectors: an interim analysis of a randomized controlled phase 3 study in Russia. Lancet. 2021; 397 (10275): 671- 681. doi: 10.1016 / S0140-6736 (21) 00234-8

This article originally appeared on Infectious Disease Advisor

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